1. Field of the Invention
The invention relates to a chip array structure for laser diodes, and more particularly to the chip array structure on the same semiconductor chip that includes at least one insulation wall to separate plural light-emitting elements originally in an array arrangement into a number of isolated light-emitting districts. In this invention, each of the light-emitting districts is corresponding to an individual wire bond area (welding pad) so as to achieve a homogeneous illumination effect by mixing lights from different light-emitting districts. Also, the illumination pattern of the laser diode can be further adjusted by appropriate current controls.
2. Description of the Prior Art
Recently in the art, light-communication technology has become one of the mainstream frames for constructing advanced networking. It is already feasible in the future that data transmission can be completely fulfilled by a light-based network. To enhance performance of the light transmission, various semiconductor laser devices have become the devoted topics for the related manufacturers and researchers in the art. Plenty of those laser devices already in the market place include the vertical cavity surface emitting Laser (VCSEL), the horizontal cavity surface emitting Laser (HCSEL), the resonant cavity light emitting diode (RCLED) and so on.
Referring to FIG. 1, a top view of a conventional laser diode array chip is schematically shown. In the laser diode array chip 9, plural laser diodes 92 are mounted to the same semiconductor chip 91 in an array arrangement by a semiconductor manufacturing process. A bonding pad 93 located at a lateral side of the array of the laser diodes 92 is electrically connected with each of the laser diodes 92 through a connection electrode 94. In the art, the single bonding pad 93 constructs the common wire bond area for all the laser diodes 92. Even in an alternative design not shown herein, these laser diodes 92 are electrically integrated through bifurcated bonding pads from the same wire bond area. In those conventional designs, currents distributed to the laser diodes 92 on the single bonding pad 93 or the common wire bond cannot be comfortably equalized. In particular, the current decaying rate as well as the electric stability might be significantly varied between the near-side diodes 92 and the far-side diodes 92 with respect to the same bonding pad 93. Thereby, the shortcoming of uneven light powers and performances is inevitable. In addition, for all the laser diodes 92 are mounted on the same bonding pad 93, an equivalent resonant effect can be induced so as to add comprehensive coherence to photos from various laser diodes 92. Thereupon, the conventional laser diode array chip 9 is highly possible to present a donut-type illumination pattern, which may make no difference with the illumination pattern of a single laser diode 92. Apparently, the merits from using plural diodes 92 are vanished.
Particularly, a single semiconductor laser chip to have a big number of laser elements (for example, an 8×8 array to have 64 elements, or a 16×16 array to have 256 elements) is now normal to current designs. As the conventional laser chip is packaged into a light-emitting module, the wire-bond process is usually applied to mount the laser chip onto the substrate of the light-emitting module by gold-wiring the bonding pad of the laser chip to a single electrode area or an electrode stem of the substrate. However, due to the features of high-correlated illumination patterns in the conventional laser chip design, and also to the increased instability in power supply with respect to an increased number of laser elements in a single laser chip, the uneven current flows would inevitably cause an inhomogeneous illumination problem to those laser elements. Obviously, such a performance in the laser chip is far from satisfaction, and thus a comprehensive improvement is definitely needed and urgent.